1. Field of the Invention
The invention relates generally to relatively inexpensive borehole plugs formed from toy or sport balls typically used for play such as by children and/or in sporting events, the borehole plugs particularly being used to support stemming and/or explosives within a borehole to facilitate shattering of earth formations by detonation of explosives within one or more boreholes.
2. Description of the Prior Art
Mining and earth removal operations often employ methodology known in the art as presplitting, this practice involving the shattering of earth formations in a controllable manner to facilitate the removal of overburden to expose seams of material which are to be mined. Devices have previously been available in the art to xe2x80x9cplugxe2x80x9d boreholes drilled in patterns for the practice of presplitting. Such devices have been intended to suspend explosives and/or stemming within such boreholes. Devices have also been available in the art for suspending stemming and/or explosives within boreholes intended to facilitate production blasting by various methods common in the art. A discussion of the prior art can be found in U.S. Pat. No. 5,035,286 to Fitzgibbon, Jr. relative to prior art previously available in the mining and earth removal industries. This patent also comprises prior art relative to the present invention. Further, the disclosure of U.S. Pat. No. 5,035,286 is incorporated hereinto by reference. Further, the disclosures of U.S. Pat. Nos. 4,913,233; 4,919,203; 5,000,261 and 5,273,110 are also incorporated hereinto by reference, these patents having the same inventor as the present patent application and common ownership with the present patent application.
Also incorporated hereinto by reference is U.S. Pat. No. 3,357,193, also to Fitzgibbon, Jr., which patent discloses temporary closure devices for boreholes, the devices being formed as inflatable, tubular structures which are inserted in a deflated condition into the upper end of a borehole and inflated therein in order to temporarily close off the hole to prevent ingress of water, to prevent ice formation within the hole and to prevent blockage of the hole by undesirable material which can fall into an open borehole. The devices of this patent further act to prevent personnel from stepping into or falling into such holes with resulting injury.
On recognition of the value of the technology disclosed in the aforesaid patents, the industry has attempted to identify inexpensive alternatives to the particular inflatable devices described in the aforesaid patents, the devices of the patents being formed of materials and through the use of methodology which has resulted in inflatable borehole plugs of exceptional reliability. The borehole plugs provided according to the aforesaid patents were found to be rapidly and conveniently useable in field blasting operations, the said borehole plugs being repositionable as desired within a borehole in the event that initial positioning within the borehole was not satisfactorily accomplished or the initial position was not the most desirable location for the plug. While the borehole plugs configured according to the aforesaid patents are relatively inexpensive in view of their value in the shattering of earth formations, practitioners in the art have continually attempted to form such borehole plugs from exceedingly cheap materials, such as the xe2x80x9crubbersxe2x80x9d used to manufacture ordinary playground balls or the like. While certain of these inflatable playground balls have functioned within certain environments at least a certain percentage of the time, these insubstantial devices have not proven to be satisfactory due to the large percentage of these devices which lose pressure once inflated within a borehole and thus have to be replaced if the user is fortunate enough to have avoided placement of stemming or explosives on top of such devices. Failure of these prior devices to maintain pressure once stemming or explosives or the like have been deposited within a borehole results in loss of the borehole and any value of the explosives and/or stemming or the like in subsequent blasting operations. The present invention particularly intends the fabrication of borehole plugs formed of plug wall materials of lesser quality than has previously been permissible with necessary reliability, the borehole plugs according to the invention being improved through reinforcement which permits the present plugs to function properly and with desired reliability within the harsh confines of a borehole wherein walls of the borehole contain irregular and jagged rock and earth surfaces and projections from said surfaces. The present devices thus constitute a significant and substantial advance in the art.
The inflatable devices of the invention suspend explosives and/or stemming materials within boreholes formed in earth formations to allow practice of methods for shattering the earth formations to effect presplitting or earth removal inter alia. The inflatable devices of the invention are positioned within boreholes in a deflated condition and are inflated at the desired locations within the hole to seal or xe2x80x9cplugxe2x80x9d the hole for support of explosive columns and/or stemming columns. The inflatable devices are formed according to the invention of common toy or sport balls of differing diameter and which are further provided with a reinforcing scrim disposed over inner wall surfaces thereof, the structure being completed by provision of an inner elastomeric layer which acts along with the toy or sport ball outer layer to sandwich the scrim therebetween the thus reinforce the inflatable device so formed. Use of the toy or sport ball itself without further improvement according to the invention results in production of an inflatable device essentially formed of a xe2x80x9crubberxe2x80x9d material or other elastomeric material which is extraordinarily susceptible to deflation within the environment of a borehole, it being necessary for an adequate inflatable device to support columns of explosives and/or stemming which can weigh many tons. Even though the toy or sport ball itself may be thicker than the materials used to form the inflatable devices particularly described in U.S. Pat. No. 5,035,286, for example, these toy or sport balls are not adequate to the intended use since said balls do not have the capability to stretch to a degree sufficient to cause the inflatable device so formed to be firm within the borehole and yet resist continued stretching, particularly in directions along the longitudinal axis of the borehole which causes an unacceptable number of such devices to fail.
While inflatable devices configured according to the invention can be formed with gas or foam generating materials sealed within said inflatable devices, it is preferred to form the inflatable devices of the invention with valves which allow inflation of the devices through hoses connected to the valves while the devices are in place within the boreholes. Valves such as tire valves, oral valves, needle valves and the like are useful. However, it is to be noted that valves such as needle valves are self-sealing and are readily connected to and disconnected from an air line such that the device can be lowered down into a borehole, inflated and then readily released from the air line. The use of certain types of valves, such as oral valves, typically require a protective flap when used with the devices of the invention.
The devices of the invention can be formed in differing sizes to accommodate boreholes of differing diameter. When used for presplitting with holes of relatively smaller diameter, columns of explosives or stemming are of lesser total weight than is the case with presplitting and production boreholes of diameters of nine inches or greater where explosive or stemming columns can weigh substantially more.
The scrim employed for reinforcement of the present inflatable devices is preferably chosen to be a nonwoven material formed of filamentary elements having high tensile strength, that is, the greatest strength of the filamentary elements are along the longitudinal axis of the filamentary material. It can thus be said that the filamentary material is anisotropic. While a single xe2x80x9cfilamentxe2x80x9d could theoretically be used to form a reinforcing scrim for a single inflatable device according to the invention, it is to be realized that in practice a multiplicity of such filaments would be laid down in a random pattern in order to form the reinforcing scrim. Nonwoven scrim such as described is of particular utility due to cost and due to realization of the advantages of the anisotropic character of the filamentary material itself. Forces transmitted through the exterior wall of the inflatable device of the invention are directed along the length of the filaments and are thus accommodated by the high tensile strength of the filaments. The inner elastomeric layer of an inflatable device configured according to the invention acts to hold the reinforcing scrim adjacent to the outer covering, that is, the playground ball portion, of the device.
It is to be understood that the present inflatable devices can be provided with reinforcement of other description including woven materials formed of filaments having high anisotropic characteristics, anisotropic whisker materials and even patterns of filamentary materials regularly laid down at given angles including right angles to each other and having spacings therebetween, these patterns of substantially anisotropic material being held adjacent the outer covering of the inflatable device by means of the inner layer of rubberized or elastomeric material. The reinforcing structure is thus held in a xe2x80x9csandwichxe2x80x9d fashion between outer and inner layers which are stretchable due to the rubberized nature or elastomeric nature of the materials from which formed.
The weight of certain of the plugs configured according to the invention can cause an inflation needle normally inserted into a valve of the plug to pull loose from the valve during lowering of the plug into a borehole. As is usual in the art, a plug is suspended on the free end of an inflation hose through the agency of an inflation needle received into the valve formed in the inflatable plug, the needle being connected to the free end of the inflation hose. In order to prevent pulling out of the inflation needle from the valve which can occur in hot climates, in particular, a friction adapter preferably formed of rubber or the like is used to prevent slippage of the plug and is connected to the plug at least during lowering of the plug into a borehole and positioning of the plug within the borehole. The adapter is essentially a rubber grommet with one end adhered to the plug above the inflation valve. The adapter has a central channel through which the inflating needle and a portion of the inflation hose extend to allow the needle to be received into the inflation valve. A U-shaped bracket attached to the end of the inflation hose at one end of the bracket attaches removable to the grommet at the other end of the bracket. The bight portion of the adapter is of a length chosen to separate the two ends of the bracket from each other according to the length of the inflation needle chosen for use. Once the plug is located within the borehole and inflated, the needle, hose and bracket can be disconnected from the grommet and thus the plug and recovered by executing a sharp jerking motion on the opposite end of the hose.
Accordingly, it is a primary object of the present invention to provide inflatable devices useful in presplitting and production blasting of earth formations, these devices exhibiting characteristics enabling a use within the environment of a borehole to suspend substantial quantities of stemming and/or explosives without deflation and with economy of material and fabrication.
It is another object of the present invention to provide inflatable devices useful in presplitting and production blasting of earth formations and having an outer covering substantially taking the form of a playground or sport ball manufactured of a rubberized or elastomeric material, the ball being reinforced internally thereof to enable its reliable use in presplitting and blasting of earth formations.
It is a further object of the invention to provide inflatable devices useful in the presplitting and production blasting of earth formations by suspension of the inflatable devices in boreholes to support stemming and/or explosives within said boreholes, the inflatable devices particularly being formed of rubberized or elastomeric toy or playground balls having a scrim reinforcement disposed internally of the ball and adjacent inner wall surfaces of said ball and held against said inner surfaces by means of an interior layer of rubberized or elastomeric material, the scrim being formed of an anisotropic material having high tensile strength.
It is another object of the invention to provide an adapter arrangement which can be joined to the plug at a location thereof surmounting a needle insertion aperture of a valve formed in the plug, the adapter arrangement providing sufficiently positive connection of the inflation needle to the plug as to allow lowering of the plug into a borehole and positioning of the plug without concern that the weight of the plug will cause the plug to slip from the needle.
Still further objects and advantages of the invention will become more readily apparent in light of the following detailed description of the preferred embodiments.